Preamble group selection in random access of wireless networks

ABSTRACT

A transport block size (TBS) of a first uplink message (RACH Msg3) transmitted on a Physical Uplink Shared Channel (PUSCH) during a random access procedure in a User Equipment (UE) accessing a radio access network may be determined by receiving a pathloss threshold parameter. A downlink pathloss value indicative of radio link conditions between the UE and a base station (eNB) serving the UE is then determined. A smaller value of TBS is selected from a set of TBS values if the determined pathloss value is greater than an operating power level of the UE minus the pathloss threshold parameter. A larger value of TBS is selected if the pathloss value is less than the operating power level of the UE minus the pathloss threshold parameter and the TBS required to transmit the RACH Msg3 exceeds the smaller TBS value.

The present application claims priority to U.S. provisional patentapplication Ser. No. 61/098,346, filed Sep. 19, 2008, and entitled“Preamble Group Selection in Random Access of Wireless Networks,” herebyincorporated herein by reference.

FIELD OF THE INVENTION

This invention generally relates to wireless cellular communication, andin particular non-synchronous random access transmission in orthogonaland single carrier frequency division multiple access (OFDMA) (SC-FDMA)systems.

BACKGROUND OF THE INVENTION

Wireless cellular communication networks incorporate a number of mobileUEs and a number of NodeBs. A NodeB is generally a fixed station, andmay also be called a base transceiver system (BTS), an access point(AP), a base station (BS), or some other equivalent terminology. Ingeneral, NodeB hardware, when deployed, is fixed and stationary, whilethe UE hardware is portable.

In contrast to NodeB, the mobile UE can be portable hardware. Userequipment (UE), also commonly referred to as a terminal or a mobilestation, may be fixed or mobile device and may be a wireless device, acellular phone, a personal digital assistant (PDA), a wireless modemcard, and so on. Uplink communication (UL) refers to a communicationfrom the mobile UE to the NodeB, whereas downlink (DL) refers tocommunication from the NodeB to the mobile UE. Each NodeB contains radiofrequency transmitter(s) and the receiver(s) used to communicatedirectly with the mobiles, which move freely around it. Similarly, eachmobile UE contains radio frequency transmitter(s) and the receiver(s)used to communicate directly with the NodeB. In cellular networks, themobiles cannot communicate directly with each other but have tocommunicate with the NodeB.

Long Term Evolution (LTE) wireless networks, also known as EvolvedUniversal Terrestrial Radio Access (E-UTRA), are being standardized bythe 3GPP working groups (WG). OFDMA and SC-FDMA (single carrier FDMA)access schemes were chosen for the down-link (DL) and up-link (UL) ofE-UTRA, respectively. User Equipments (UE's) are time and frequencymultiplexed on a physical uplink shared channel (PUSCH), and a fine timeand frequency synchronization between UE's guarantees optimal intra-cellorthogonality. In case the UE is not UL synchronized, it uses anon-synchronized Physical Random Access Channel (PRACH), and the BaseStation provides back some allocated UL resource and timing advanceinformation to allow the UE to transmit on the PUSCH. The generaloperations of the physical channels are described in the EUTRAspecifications, for example: “3rd Generation Partnership Project;Technical Specification Group Radio Access Network; Evolved UniversalTerrestrial Radio Access (E-UTRA); Physical Channels and Modulation (TS36.211 Release 8, or later).” As improvements of networks are made, theNodeB functionality evolves; a NodeB in the EUTRA environment is alsoreferred to as an evolved NodeB (eNB).

Random access transmission denotes a transmission by the mobileterminal, of at least one signal, from a plurality of pre-definedsignals. The plurality of pre-defined signals is specified by the randomaccess structure. Random access transmissions may also be referred to asranging transmissions, or any other analogous term which typicallydesignates an autonomously initiated transmission by a mobile UE. Randomaccess transmissions are incorporated in practically all wirelesscellular standards, including EUTRA, 802.16, etc.

User Equipment may be either up-link (“UL”) synchronized or ULnon-synchronized. When the UE UL has not been time synchronized, or haslost time synchronization, the UE can perform a non-synchronized randomaccess to request allocation of up-link resources. Additionally, a UEcan perform non-synchronized random access to register itself at theaccess point, or for numerous other reasons. Possible uses of randomaccess transmission are many, and do not restrict the scope of theinvention. For example, the non-synchronized random access allows theaccess point (“Node B”) to estimate, and if necessary, to adjust theUE's transmission timing, as well as to allocate resources for the UE'ssubsequent up-link transmission. Resource requests from ULnon-synchronized UEs may occur for a variety of reasons, for example:new network access, data ready to transmit, or handover procedures. ANode B is generally a fixed station and may be called a base transceiversystem (BTS), an access point, a base station, or various other names.

As wireless systems proliferate, the expanding user base and the demandfor new services necessitate the development of technologies capable ofmeeting users' ever increasing expectations. Users of mobiletelecommunications devices expect not only globally available reliablevoice communications, but a variety of data services, such as email,text messaging, and internet access. These factors conjoin to compelcollaboration between telecommunications service providers in thedevelopment of advanced telecommunications technologies.

Consequently, the random access channel is intended to encompass a widerrange of functionalities than in previous or current cellular networks,thus increasing its expected load. Further, the random access signal,through which the UE initiates the random access procedure, mustreliably accommodate variable cell sizes, and provide the Node B withsufficient information to effectively prioritize resource requests.Also, because of its potentially non-synchronized nature, the randomaccess signal must be designed to minimize interference with other UL(nearly) orthogonal transmissions.

The random access signal is based on a preamble based physical structureof the PRACH. A number of available preambles are provided that can beused concurrently to minimize the collision probability between UEsaccessing the PRACH in a contention-based manner. The signatures forrandom access preambles are partitioned into two configurable-sizegroups, enabling carrying 1-bit of information on the preamble. Thisinformation indicates to the eNB the preferred size of the firstpost-preamble PUSCH transmission, chosen by the UE from among twopossible sizes based on the amount of data available for transmissionand the radio conditions. 3GPP Document R1-083476 suggests use of aPathloss measurement as a radio-link metric for preamble group selectionin the Random Access procedure.

BRIEF DESCRIPTION OF THE DRAWINGS

Particular embodiments in accordance with the invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings, in which:

FIG. 1 shows an illustrative telecommunications network;

FIG. 2 shows an illustrative up-link time/frequency allocation;

FIG. 3 shows illustrative 1 and 2 sub-frame random access signals;

FIG. 4 shows a first illustrative embodiment of random access signaltransmitter;

FIG. 5 shows a second illustrative embodiment of a random access signaltransmitter;

FIG. 6 shows a third illustrative embodiment of a random access signaltransmitter;

FIG. 7 shows an illustrative non-synchronous random access signalreceiver;

FIG. 8 shows a flow diagram of an illustrative random access preamblesignal length adjustment and transmission method;

FIG. 9 shows a flow diagram of an illustrative alternative random accesspreamble signal length adjustment and transmission method; and

FIG. 10 is a block diagram of an exemplary UE and NodeB for use in thenetwork of FIG. 1.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Most of the time, the eNB is not aware of the use-case that triggered aRandom Access procedure, nor is it aware of the UE's buffer status. Inabsence of any information, the eNB can only allocate blindly one singlestandard resource for the first transmission on the PUSCH following asuccessful RACH preamble attempt, also referred to as message 3 of theRandom Access procedure. The maximum message 3 size a cell-edge UE canafford in the worst-case coverage situation is 80 bits. It is generallyagreed that this particular transmission sets the limits of the overallLTE UL coverage. However, even in such a scenario, it would beunnecessarily restrictive to impose this unique minimum transport blocksize (TBS) for message 3 to all UEs in the cell. As a result, twomessage sizes, or TBSs, are considered for message 3, namely a “smaller”message size, MESSAGE_SIZE_GROUP_A, and a “larger” message size,MESSAGE_SIZE_GROUP_B, as defined in 3GPP TS 36.321, TechnicalSpecification Group Radio Access Network; Evolved Universal TerrestrialRadio Access (E-UTRA); “Medium Access Control (MAC) protocolspecification (Release 8).” Only MESSAGE_SIZE_GROUP_A needs to be eitherbroadcast on a system information block (SIB) or hard-coded in thespecification. The UE indicates which of the two TBSs is moreappropriate based on both the amount of data available for transmissionand the radio conditions. For the latter aspect, it is agreed that thePathloss measurement would be used as radio-link metric. The powercontrol setting of message 3, can be summarized as follows:

$\begin{matrix}{P_{{msg}\; 3} = {\min\begin{Bmatrix}{P_{MAX};{{10\mspace{14mu}{\log_{10}\left( N_{RB} \right)}} + P_{0\;\_\;{PRE}} +}} \\{\Delta_{{PREAMBLE} - {{Msg}\; 3}} + {PL} + \Delta_{TF} + {\Delta\; P_{rampup}} + \delta_{{msg}\; 2}}\end{Bmatrix}}} & (1)\end{matrix}$where:P_(msg3) is the UE's transmit power for message 3 transmissionP_(MAX) is the maximum allowed power that depends on the UE power classN_(RB) is the number of RBs allocated on PUSCH to message 3P₀ _(—) _(PRE) is the initial target received preamble power at eNBantenna portΔ_(PREAMBLE-Msg3) is the nominal power gap between the preamble andmessage 3, signaled by the eNBPL is the downlink pathloss estimate calculated in the UEΔP_(rampup) is the power offset reflecting the accumulated optionalpower rampup of the preamble during potential retriesδ_(msg2) is the TPC command indicated in the random access responseΔ_(TF) is an optional MCS-dependent power offset defined as:

$\begin{matrix}\left\{ \begin{matrix}{\Delta_{TF} = {10\mspace{14mu}{\log_{10}\left( {2^{1.25{MPR}} - 1} \right)}}} \\{{{MPR} = {{TBS}/N_{RE}}}\mspace{121mu}} \\{{N_{RE} = {2{N_{RB} \cdot N_{sc}^{RB} \cdot N_{symb}^{UL}}}}\mspace{45mu}}\end{matrix}\; \right. & (2)\end{matrix}$where:MPR is the modulation power ratio,N_(RE) is the number of resource elements available in the allocatedmessage 3 resource.Δ_(TF) is a function of both the TBS and the number of allocated RBs.

The aim of setting the TBS of message 3 based on radio-link conditionsis to prevent from choosing larger message 3 TBS, MESSAGE_SIZE_GROUP_B,leading to a required transmit power exceeding the maximum allowedpower, P_(MAX). In other words, the larger message 3 size,MESSAGE_SIZE_GROUP_B, should only be selected by the UE under thefollowing condition:10 log₁₀(N _(RB) _(—) ₂)+P ₀ _(—) _(PRE)+Δ_(PREAMBLE-Msg3) +PL+Δ _(TF)_(—) ₂ +ΔP _(rampup)+δ_(msg2) <P _(MAX)  (3)where N_(RB-2) and Δ_(TF-2) are the number of RBs and the MCS-dependentpower offset of message 3 of size MESSAGE_SIZE_GROUP_B.

This translates into the following threshold on Pathloss,PARTITION_PATHLOSS_THRESHOLD, beyond which a MESSAGE_SIZE_GROUP_Apreamble group should always be selected:

$\begin{matrix}{{{PARTITION\_ PATHLOSS}{\_ THRESHOLD}} = {\underset{\underset{{known}\mspace{14mu}{before}\mspace{14mu}{msg}\; 3\mspace{14mu}{allocation}}{︸}}{P_{MAX} - P_{0\;\_\;{PRE}} - \Delta_{{PREAMBLE} - {{Msg}\; 3}}} - \underset{\underset{{unknown}\mspace{14mu}{before}\mspace{14mu}{msg}\; 3\mspace{14mu}{allocation}}{︸}}{\Delta_{{TF}\;\_\; 2} - {\Delta\; P_{rampup}} - \delta_{{msg}\; 2} - {10\mspace{14mu}{\log_{10}\left( N_{{RB}\;\_\; 2} \right)}}}}} & (4)\end{matrix}$As shown in Equation (4), part of the information related to the message3 allocation is not available at the UE when it prepares for preambletransmission, as follows:

-   -   N_(RB-2): here it is questionable why the eNB would use a        different number of RBs when allocating different messages 3 of        MESSAGE_SIZE_GROUP_B size. Practically, a common sense        allocation will consist in using 1-RB allocation for        MESSAGE_SIZE_GROUP_A and 2-RB allocation for        MESSAGE_SIZE_GROUP_B. Some flexibility may be used to allow for        different settings in different cells or at different times, but        such flexibility does not seem to be justified on a sub-frame        basis. Therefore, in at least some embodiments N_(RB-2) is        treated as a semi-static parameter in the eNB.    -   Δ_(TF-2), when applied, is a function defined by equation (2) of        MESSAGE_SIZE_GROUP_B and the number of allocated RBs for message        3, N_(RB-2), so given MESSAGE_SIZE_GROUP_B is known, by the eNB,        the same above discussion on N_(RB-2) applies.    -   ΔP_(rampup): RAN4 has specified conformance tests on the PRACH        preamble choosing an operational point for the probability of        missed detection of 1%, as defined in 3GPP TS 36.104 v8.2.0        (2008-05), Technical Specification Group Radio Access Network;        Evolved Universal Terrestrial Radio Access (E-UTRA); “Base        Station (BS) radio transmission and reception” (Release 8).        Under this assumption, only 1% of preambles will ramp-up their        power, which can be neglected here.    -   δ_(msg2): this is TPC command conveyed by Random Access Response        (RAR) that neither the UE nor the eNB can predict before        preamble transmission. Ignoring this parameter only has a        coverage impact for message 3 when δ_(msg2)>0, i.e. the TPC        requests the UE to increase its power for message 3        transmission, which may cause erroneous MESSAGE_SIZE_GROUP_B        selection when MESSAGE_SIZE_GROUP_A would have been safer.        However the percentage of occurrence of this event depends on        the range of δ_(msg2) which currently does not exceed 8 dB on        the positive side. It is believed that a cautious usage of        δ_(msg2) should be foreseen anyway as, in most practical cases,        the instantaneous fading nature of the preamble disallows any        accurate long-term power estimation. To be conservative, some        Pathloss margin should be provisioned for this potential        correction.

Therefore, the above information can be signaled by the eNB in a singleparameter not exceeding 2-3 bits, referred to as RACH_MSG3_THRESHOLD,computed as follows:RACH_MSG3_THRESHOLD=Δ_(TF) _(—) ₂+10 log₁₀(N _(RB) _(—) ₂)+margin  (5)

It follows that the resulting condition under which the UE can selectMESSAGE_SIZE_GROUP_B size for message 3 transmission is:

$\begin{matrix}\left\{ \begin{matrix}{{{PL} < {{PARTITION\_ PATHLOSS}{\_ THRESHOLD}}}\mspace{205mu}} \\{{{with}\text{:}}\mspace{664mu}} \\{{{{PARTITION\_ PATHLOSS}{\_ THRESHOLD}} =}\mspace{239mu}} \\{P_{MAX} - P_{0\_\;{PRE}} - \Delta_{{PREAMBLE}\; - {{Msg}\; 3}} - {{RACH\_ MSG3}{\_ THRESHOLD}}}\end{matrix} \right. & (6)\end{matrix}$where the terms at the right side of the equation are all available atthe UE before preamble transmission. The parameter RACH_MSG3_THRESHOLDshould not exceed 2-3 bits and is either broadcasted on SIB orhard-coded in the specification. The former case provides someflexibility to the network in using different values forMESSAGE_SIZE_GROUP_B and N_(RB-2) at different times and in differentcells. In the latter case, the value of RACH_MSG3_THRESHOLD should bespecified based on the TS 36.321 specification using a default value forMESSAGE_SIZE_GROUP_B and N_(RB-2).

In some embodiments, RACH_MSG3_THRESHOLD is referred to asmessagePowerOffsetGroupB and N_(RB-2), Δ_(TF-2) are referred to N_(RB-B)and Δ_(TF-B) respectively.

Table 1 provides a range of values of this parameter, computed accordingto Equation (7), when considering MESSAGE_SIZE_GROUP_B ranging from 104bits (1 RB, QPSK) up to 1544 bits (5 RBs, 64QAM), which is considered tobe sufficient to cover the range of message 3 TBSs when coveragerestrictions apply. This range also reflects the limited TBS range ofMsg3 (TBS index I_(TBS)≦15), resulting from the truncated modulation andcoding scheme field as defined in R2-084964/R1-083431, “LS Reply toUplink grant format in Random Access Response.” As can be observed,messagePowerOffsetGroupB ranges from 0 dB up to 12 dB, which in anexemplary embodiment of Table 1 is extended to [0, 18] dB to includesome margin.

TABLE 1 messagePowerOffsetGroupB parameter values Field value 0 1 2 3 45 6 7 Parameter value (dB) —∞ 0 3 6 9 12 15 18 Note that the value of —∞is included to be compatible with an embodiment responsive toR2-087402/R1-090003, “LS on preamble group selection based on radio linkcondition.”

Appendix A and Appendix B contain spreadsheets that illustratecalculation details that are used to select the values for Table 1.Appendix A provides a detailed range of values formessagePowerOffsetGroupB while Appendix B shows the benefit of thepreamble group selection, and shows the limit where the maximum Tx poweris reached when transmitting the larger message size, which is the limitby which UE should select the smaller message size.

FIG. 1 shows an exemplary wireless telecommunications network 100. Theillustrative telecommunications network includes base stations 101, 102,and 103. Each of base stations 101, 102, and 103 are operable overcorresponding coverage areas 104, 105, and 106. Each base station'scoverage area is further divided into cells. In the illustrated network,each base station's coverage area is divided into three cells. Handsetor other UE 109 is shown in Cell A 108, which is within coverage area104 of base station 101. Base station 101 is transmitting to andreceiving transmissions from UE 109. As UE 109 moves out of Cell A 108,and into Cell B 107, UE 109 may be handed over to base station 102.Because UE 109 is synchronized with base station 101, UE 109 can employnon-synchronized random access to initiate handover to base station 102.

The UE 109 can also employ non-synchronous random access to requestallocation of up-link 111 time or frequency or code resources. If UE 109has data ready for transmission, for example, traffic data, measurementsreport, tracking area update, etc., UE 109 can transmit a random accesssignal on up-link 111. The random access signal notifies base station101 that UE 109 requires up-link resources to transmit its data. Basestation 101 responds by transmitting to UE 109, via down-link 110, amessage containing the parameters of the resources allocated for UE 109up-link transmission along with a possible timing error correction.After receiving the resource allocation and a possible timing advancemessage transmitted on down-link 110 by base station 101, UE 109(possibly) adjusts its transmit timing and transmits its data on up-link111 employing the allotted resources during the prescribed timeinterval.

For a random access transmission, UE 109 selects a message 3 size to beconveyed to the NodeB by the random access signal as described above andwith regard to equation 6.

FIG. 2 illustrates an exemplary up-link transmission frame 202, and theallocation of the frame to scheduled and random access channels. Theillustrative up-link transmission frame 202, comprises a plurality oftransmission sub-frames. Sub-frames 203 are reserved for scheduled UEup-link transmissions. Interspersed among scheduled sub-frames 203, aretime and frequency resources allocated to random access channels 201. Inthe illustration of FIG. 2, a single sub-frame supports two randomaccess channels. Note that the illustrated number and spacing of randomaccess channels is purely a matter of convenience; a particulartransmission frame implementation may allocate more or less resources torandom access channels. Including multiple random access channels allowsmultiple UEs to simultaneously transmit a random access signal withoutcollision. However, because each UE independently chooses the randomaccess channel on which it transmits, collisions between UE randomaccess signals may occur and must be resolved.

FIG. 3 illustrates one embodiment of a random access signal. Randomaccess signal 301 occupies a single sub-frame 308, while random accesssignal 311 occupies two sub-frames 318. In the illustrative embodimentof one sub-frame random access signal 301, duration 302 is includedprior to transmission of random access preamble signal 304, to preventinterference between random access preamble signal 304 and anytransmission on the random access preamble signal frequency bands duringthe previous sub-frame. This duration 302 may or may not be realized asa cyclic prefix (“CP”) attached at the preamble start to allowsimplified frequency-domain receiver implementation. Random accesspreamble signal 304 follows duration 302. Random access preamble signal304 is designed to maximize the probability of preamble detection by theNode B and to minimize the probability of false preamble detections bythe Node B, while maximizing the total number of resource opportunities.Similarly random access signal 311 includes cyclic prefix 312 andpreamble 314 occupy two sub-frames 318.

Embodiments of the invention utilize CAZAC sequences to generate therandom access preamble signal. CAZAC sequences are complex-valuedsequences with following two properties: 1) constant amplitude (CA), and2) zero cyclic autocorrelation (ZAC). Well-known examples of CAZACsequences include (but are not limited to): Chu Sequences, Frank-ZadoffSequences, Zadoff-Chu (ZC) Sequences, and Generalized Chirp-Like (GCL)Sequences.

As is well known in the art, Zadoff-Chu (ZC) sequences, as defined by:aM(k)=exp[j2π(M/N)[k(k+1)/2+qk]] for N oddaM(k)=exp[j2π(M/N)[k2/2+qk]] for N even

are representative examples of CAZAC sequences. Alternative conventionfor ZC definition replaces “j” in the above formula by “−j.” Eitherconvention can be adopted. In the above formula, “M” and “N” arerelatively prime, and “q” is any fixed integer. Also, “N” is the lengthof the sequence, “k” is the index of the sequence element (k is from {0,1, . . . , N−1}), and “M” is the index of the root ZC sequence. Making“N” a prime number maximizes the set of non-orthogonal root ZC sequenceshaving optimal cross-correlation. Thus, when “N” is prime, there are“(N−1)” possible choices for “M,” where each choice results in adistinct root ZC CAZAC sequence. In this invention, terms: Zadoff-Chu,ZC, and ZC CAZAC, are used interchangeably. Term CAZAC denotes any CAZACsequence, like ZC, or otherwise.

In this disclosure, the cyclically shifted or phase ramped CAZAC-likesequence is sometimes denoted as cyclic shifted base sequence, cyclicshifted root sequence, phase ramped base sequence, phase ramped rootsequence, or any other equivalent term.

In one embodiment of the invention, random access preamble signal 304(or 314) is constructed from a constant amplitude zero autocorrelation(“CAZAC”) sequence, such as a ZC sequence. Additional modifications tothe selected CAZAC sequence can be performed using any of the followingoperations: multiplication by a complex constant, DFT, IDFT, FFT, IFFT,cyclic shifting, zero-padding, sequence block-repetition, sequencetruncation, sequence cyclic-extension, and others. Thus, in the primaryembodiment of the invention, a UE constructs random access preamblesignal (304 or 314), by selecting a CAZAC sequence, possibly performinga combination of described modifications to the selected CAZAC sequence,modulating the modified sequence, and transmitting the resulting randomaccess signal over the air.

In practical systems, there is a need to specify or pre-define the setof allowed random access preamble signals. Thus, a UE autonomouslyselects (or can be allocated) at least one random access preamble signalfrom the pre-defined set of random access preamble signals.Consecutively, UE transmits the selected signal over the air. Node Bsearches within the finite pre-defined set of random access signals, andis therefore able to detect an occurrence of a random accesstransmission by the UE.

One method of pre-defining the set of random access preamble signals isto allow a choice of modifications to a fixed root CAZAC sequence, suchas a ZC CAZAC sequence. For example, in one embodiment of the invention,distinct random access preamble signals are constructed by applyingdistinct cyclic shifts when performing the modification of a root CAZACsequence. Thus, in this embodiment of the invention, UE autonomouslyselects the random preamble access signal by selecting a value for thecyclic shift. The selected value of the cyclic shift is applied duringthe process of modification of the root CAZAC sequence. For sequence[c(0) c(1) c(2) . . . c(L−1)], the corresponding cyclically shiftedsequence is [c(n) c(n+1) c(n+2) . . . c(L−1) c(0) c(1) . . . c(n−1)],where “n” is the value of the cyclic shift. Thus, in this embodiment,the set of possible cyclic shifts defines the set of allowed randomaccess preamble signals.

An alternate method of pre-defining the set of random access preamblesignals is to permit a choice of used root CAZAC sequences, such as ZCsequences. For example, in this embodiment of the invention, distinctrandom access preamble signals are constructed by applying pre-definedcommon modifications to distinct root CAZAC sequences. Consequently, UEautonomously selects the random access preamble signal by selecting adistinct root CAZAC sequence, which it (UE) then modifies to produce therandom access preamble signal. Thus, in this alternate embodiment of theinvention, the set of allowed root CAZAC sequences also defines the setof allowed random access preamble signals.

In a general embodiment of the invention, the set of allowed randomaccess preamble signals is defined by two sets: 1) set of allowed rootCAZAC sequences, and 2) set of allowed modifications to a given rootCAZAC sequence. For example, in this general embodiment of theinvention, a random access preamble signal is constructed by firstselecting the root ZC CAZAC sequence, and second, by selecting the valueof the cyclic shift. Selections can be performed autonomously by the UE,and the UE applies the selected value of the cyclic shift during theprocess of modification of the selected root ZC CAZAC sequence.

FIG. 4 is a block diagram showing an apparatus in accordance with anembodiment of the invention. Apparatus 400 comprises ZC Root SequenceSelector 401, Cyclic Shift Selector 402, Repeat Selector 403, ZC RootSequence Generator 404, Cyclic Shifter 405, DFT 406, Tone Map 407, othersignals or zero-padding in 411, IDFT 408, Repeater 409, optionalrepeated samples 412, Add CP 410, and the random access signal 413.Elements of the apparatus may be implemented as components in aprogrammable processor. At times, the IDFT block in 408 may beimplemented using an Inverse Fast Fourier Transform (IFFT), and at timesthe DFT block 406 may be implemented using Fast Fourier Transform (FFT).Apparatus 400 is used to select and perform the random access preamblesignal transmission as follows. The UE performs selection of the ZCCAZAC root sequence using ZC Root Sequence Selector 401 and theselection of the cyclic shift value using 402. Next, UE generates the ZCsequence using ZC Root Sequence Generator 404. Then, if necessary, theUE performs cyclic shifting of the selected ZC sequence using CyclicShifter 405. The UE performs DFT (Discrete Fourier Transform) of thecyclically shifted ZC sequence DFT 406. The result of the DFT operationis mapped onto designated set of tones (sub-carriers) using Tone Map407. Additional signals or zero-padding signals 411, may or may not bepresent. The UE next performs IDFT of the mapped signal using IDFT 408.Size of the IDFT 408 can be bigger than the size of DFT 406.Block-Repetition of the IDFT-ed signal is optional, and performed usingRepeater 409. Note that signals 412 represent optional repeated samples.This repetition can be applied when the preamble transmission occupiestwo or more sub-frames. An optional cyclic prefix (CP) can then be addedusing Add CP 410, to arrive at the random access signal 413. The randomaccess signal 413 is transmitted over the air.

FIG. 5 is a block diagram showing an apparatus in accordance with analternative embodiment of the invention. Apparatus 500 comprises ZC RootSequence Selector 501, Cyclic Shift Selector 502, Repeat Selector 503,ZC Root Sequence Generator 504, Cyclic Shifter 505, DFT 506, Tone Map507, other signals or zero-padding 511, IDFT 508, Repeater 509, optionalrepeated samples 512, Add CP 510, and the random access signal 513.Elements of the apparatus may be implemented as components in aprogrammable processor. At times, the IDFT 508 may be implemented usingan Inverse Fast Fourier Transform (IFFT), and at times the DFT 506 maybe implemented using Fast Fourier Transform (FFT). Apparatus 500 is usedto select and perform the random access preamble signal transmission asfollows. The UE performs selection of the ZC CAZAC root sequence usingZC Root Sequence Selector 501 and the selection of the cyclic shiftvalue using Cyclic Shifter 502. Then, UE generates the ZC sequence usingZC Root Sequence Generator 504. The selected ZC sequence is transformedusing DFT 506. The result of the DFT operation is then mapped ontodesignated set of tones (sub-carriers) using Tone Map 507. Additionalsignals or zero-padding 511, may or may not be present. The UE thenperforms IDFT of the mapped signal using IDFT 508. Using Cyclic Shifter505, the selected value of the cyclic shift is then applied to theIDFT-ed signal. The value of the cyclic shift is obtained from 502.Block-Repetition of the cyclically shifted IDFT-ed signal is optional,and performed using 509. Note that 512 represent optional repeatedsamples. This repetition can be applied when the preamble transmissionoccupies two or more sub-frames. An optional cyclic prefix (CP) can thenbe added using 510, to arrive at the random access signal 513. Therandom access signal 513 is transmitted over the air.

FIG. 6 is a block diagram showing an apparatus in accordance with athird embodiment of the invention. Apparatus 600 comprises ZC RootSequence Selector 601, Cyclic Shift Selector 602, Repeat Selector 603,ZC Root Sequence Generator 604, Cyclic Shifter 605, Tone Map 607, othersignals or zero-padding in 611, IDFT 608, Repeater 609, optionalrepeated samples 612, Add CP 610, and the random access signal 613.Elements of the apparatus may be implemented as components in aprogrammable processor. At times, the IDFT block 608 may be implementedusing an Inverse Fast Fourier Transform (IFFT). Apparatus 600 is used toselect and perform the random access preamble signal transmission asfollows. The UE performs selection of the ZC CAZAC root sequence usingZC Root Sequence Selector 601 and the selection of the cyclic shiftvalue using Cyclic Shift Selector 602. Then, UE generates the ZCsequence using ZC Root Sequence Generator 604. Selected ZC sequence ismapped onto designated set of tones (sub-carriers) using Tone Map 607.Additional signals or zero-padding signals 611, may or may not bepresent. The UE then performs IDFT of the mapped signal using IDFT 608.Using Cyclic Shifter 605, the selected value of the cyclic shift isapplied to the IDFT-ed signal. Value of the cyclic shift is obtainedfrom Cyclic Shift Selector 602. Block-Repetition of the cyclicallyshifted IDFT-ed signal is optional, and performed using Repeater 609.Note that signals 612 represent optional repeated samples. Thisrepetition can be applied when the preamble transmission occupies two ormore sub-frames. An optional cyclic prefix (CP) can then be added usingAdd CP 610, to arrive at the random access signal 613. The random accesssignal 613 is then transmitted over the air.

In all embodiments of the invention, the set of allowed cyclic shiftscan be dimensioned in accordance with the physical limitations of thecell, which include cells maximum round trip delay plus the delay spreadof the channel. For example, a single root ZC CAZAC sequence may becyclically shifted by any integer multiple of the cell's maximum roundtrip delay plus the delay spread, to generate a set of pre-definedrandom access preamble signals. The maximum round trip delay plus thedelay spread of the channel must be converted to the sampling unit ofthe sequence. Thus, if the maximum round trip plus the delay spread ofthe channel is given as “x,” then possible choices for cyclic shiftvalues can be dimensioned as n from {0, x, 2x, . . . , (u−1)x} where uxcan't exceed the length of the sequence which is being cyclicallyshifted.

Round trip delay is a function of cell size, where cell size is definedas the maximum distance d at which a UE can interact with the cell'sbase station, and can be approximated using the formula t=6.67d, where tand d are expressed in μs and km respectively. The round-trip delay isthe delay of the earlier radio path. A typical earlier path is theline-of-sight path, defined as the direct (straight-line) radio pathbetween the UE and the base station. When the UE is surrounded byreflectors, its radiated emission is reflected by these obstacles,creating multiple, longer traveling radio paths. Consequently, multipletime-delayed copies of the UE transmission arrive at the base station.The time period over which these copies are delayed is referred to as“delay spread,” and for example, in some cases, 5 μs may be considered aconservative value thereof.

When the set {0, x, 2x, . . . , (u−1)x} of cyclic shift values generatesan insufficient number of distinct random access preamble signals, thenadditional root ZC CAZAC sequences (for example, for M=2 and M=3) can beemployed for random access preamble signal generation. In thissituation, selection of prime N shows to be advantageous, because inthat case, the set of all possible choices for M is {1, 2, . . . ,(N−1)}. Thus, in one embodiment of the invention, distinct random accesspreamble signals are identified by the set of all possible choices forthe cyclic shift value and the set of allowed choices for M. In additionto providing supplementary intra-cell sequences, when used inneighboring cells, these additional root ZC CAZAC sequences provide goodinter-cell interference mitigation. Thus, during the cellular systemdesign, a scenario where adjacent cells use identical root sequencesshould be avoided. This can be achieved through a number of possibletechniques, including but not limited to: cellular system planning,sequence hopping, or a combination thereof.

The set of allowed random access preamble signals must be revealed tothe UE prior to the random access transmission. This can be achieved ina number of different ways, including hard-wiring this information inthe UE. The preferred approach, however, is for the Node B to broadcastinformation which allows the UE to infer the set of allowed randomaccess preamble signals. For example, the Node B can broadcast: 1) whichroot CAZAC sequences are permitted, and 2) which values of the“cyclic-shift” are permitted. The UE reads the broadcasted information,infers the allowed set of random access preamble signals, selects atleast one signal from the set, and performs the random accesstransmission. Note that the selection of the random access preamblesignal amounts to the selection of the root ZC CAZAC sequence, theselection of the value of the cyclic shift, and possibly the selectionof the frequency bin (in case multiple bins are configured per randomaccess time slot). In certain cases, additional broadcasted informationmay be required, such as whether or not the UE needs to perform signalrepetition of or not. Overall, this approach, based on broadcasting therequired information, is preferred, because it allows for optimizing thecellular network based on physical limitations, such as the cell-size.Any given UE is then flexible enough to be used in all types of cells,and system optimization is performed by the cell design.

Sequences obtained from cyclic shifts of a single CAZAC root sequence(ZC or otherwise) are orthogonal to one another if the cyclic shiftvalue is larger than the maximum time uncertainty of the receivedsignal, including the delay spread and the spill-over. In other words,the cyclic shifts create zones with zero correlation between distinctrandom access preamble signals. Thus, a cyclically shifted sequence canbe observed without any interference from sequences created usingdifferent cyclic shifts. Sequences obtained from cyclic shifts ofdifferent Zadoff-Chu (ZC) sequences are not orthogonal, but have optimalcross-correlation as long as the sequence length is a prime number.Therefore, it is recommended that orthogonal sequences should be favoredover non-orthogonal sequences. For this reason, additional Zadoff-Chu(ZC) root sequences should be used only when the required number ofsequences cannot be generated by cyclic shifts of a single rootsequence. As a result, cyclic shift dimensioning is of primaryimportance in the random access sequence design. As mentioned above, thecyclic shift value is dimensioned to account for the maximum timeuncertainty in random access preamble reception. This time uncertaintyreflects the Node B-UE-Node B signal propagation delay (“round-triptime”) plus the delay spread. Thus, cyclic shift dimensioning ensuresthat distinct random access signals, generated from a single root CAZACsequence, are received within the zone of zero mutual correlation.Although delay spread can be assumed to be constant, signal round-triptime depends on the cell size. Thus, the larger the cell, the larger thecyclic shift required to generate orthogonal sequences, andcorrespondingly, the larger the number of Zadoff-Chu (ZC) root sequencesnecessary to provide the required number of sequences.

Table 2 provides an example of random access preamble sequence designfor different cell sizes. Table 2 illustrates how the number of requiredroot ZC CAZAC sequences increases from 1 to 8, when the cell size isincreased from 0.8 km (Cell Scenario 1) to 13.9 km (Cell Scenario 4).Table 2 is derived using following parameters: Maximum delay spread is 5μsec, root ZC CAZAC sequence length is 863 samples, preamble samplingrate is 1.07875 MHz, and spill-over guard period is 2 samples. Becausethe expected inter-cell interference and load (user density) increasesas cell size decreases, smaller cells need more protection fromco-preamble interference than larger cells. Thus, the relationshipbetween cell size and the required number of Zadoff-Chu (ZC) rootsequences allows for system optimization, and the Node B shouldconfigure the primitive cyclic shift to be used in each cellindependently. The set of used cyclic shifts values is then built asintegral multiples of the primitive cyclic shift value. As shown inTable 2, this can be done either by configuring either the primitivecyclic shift value, or by configuring the number of different rootZadoff-Chu (ZC) sequences to be used in a cell. This configurabilityprovides the benefit of providing a constant number of distinct randomaccess preamble signals irrespective of the cell size, which simplifiesthe specification of the Medium Access Control (MAC) procedure

TABLE 2 Cell Scenarios With Respect to Different Cyclic Shift IncrementsNumber of Distinct Random Number Of Primitive Access Used Root ZC Numberof Used Cyclic Cellular Cell Size Preamble CAZAC Cyclic Shifts Per ShiftValue Scenario Index [km] Signals Sequences ZC Sequence [samples] 1 0.864 1 64 13 2 2.6 64 2 32 26 3 6.3 64 4 16 53 4 13.9 64 8 8 107

FIG. 7 shows an embodiment of a random access signal receiver. Thisreceiver advantageously makes use of the time and frequency domaintransforming components used to map and de-map data blocks in theSC-FDMA up-link sub-frame. The received random access signal 701comprising cyclic prefix and random access preamble signal is input tocyclic prefix removal component 702 which strips cyclic prefix from therandom access signal producing signal 703. Frequency domain transformingcomponent 704 is coupled to cyclic prefix removal component 702.Frequency domain transforming component 704 converts signal 703 intosub-carrier mapped frequency tones 705. Sub-carrier de-mapping component706 is coupled to frequency domain transforming component 704.Sub-carrier de-mapping component 706 de-maps sub-carrier mappedfrequency tones 705 to produce useful frequency tones 707. Productcomponent 711 is coupled to both sub-carrier de-mapping component 706and the complex conjugation component 709. Frequency domain transformingcomponent 709 converts a preamble root sequence 710, such as a primelength Zadoff-Chu sequence, into a corresponding set of preamblefrequency tones 708. Product component 711 computes a tone by tonecomplex multiplication of received frequency tones 707 with samples 708to produce a set of frequency tones 712. Time domain transformingcomponent 713 is coupled to product component 711. Time domaintransforming component 713 converts multiplied frequency tones 712 intocorrelated time signal 714. Correlated time signal 714 containsconcatenated power delay profiles of all cyclic shift replicas of thepreamble root sequence 710. Energy detection block 715 is coupled totime domain transforming block 713. Energy detection block 715identifies received preamble sequences by detecting the time of peakcorrelation between received random access signal 701 and preamble rootsequence 710. Note that DFT 709 is required when the correspondingtransmitter diagram is given as in either FIG. 4, or as in FIG. 5. Incase that transmitter diagram is as in FIG. 6, the DFT 709 is omitted.

As pointed out earlier, a prime length preamble sequence is recommendedfor use with the SC-FDMA up-link transmitter system. To achieve this,following steps can be taken. Preamble duration Tp is selected tooptimize cell coverage (cell size, noise and interference conditions),and to be an integer multiple of the SC-FDMA data block duration. Areference length Npi=Tp×Rsi samples is selected, where Rsi is theallocated random access signal bandwidth, which is not used by datatransmissions. Preamble sequence is then generated with sequence lengthcorresponding to the largest prime number Np which is less thanreference length Npi. Thus, since preamble duration remains Tp, preamblesampling rate becomes Rsi×Np/Npi. Because Npi sub-carriers are allocatedto the random-access channel, and the preamble was shortened to thenearest lower prime number of samples (Np), there are unusedsub-carriers that may be zeroed and distributed outside the preamblesub-carriers to isolate the preamble from the surrounding frequencybands.

FIG. 8 shows a flow diagram of an illustrative method for constructing aprime length sequence for use with an SC-FDMA up-link transmitter. Inblock 800, a RACH message 3 threshold value encoded as a 2 or three bitvalue is received from the serving NodeB via an SIB. The threshold valueis calculated by the NodeB as described with respect to equation 5. TheUE then uses the threshold value to determine in block 801 its requestedmessage 3 length as described in more detail with regard to equation 6.Since there are two choices for the message 3 length, the UE forms thepreamble by selecting from one of two defined sets of sequences in orderto convey the preferred message 3 size to the NodeB.

In block 802, a preamble duration T_(p) is selected. T_(p) is an integermultiple of the SC-FDMA up-link data block duration.

In block 804, a reference length is derived. This reference length isN_(pi) samples, where N_(pi)=T_(p)×R_(si), and R_(si) is the allocatedrandom access signal bandwidth. In block 806, the reference lengthderived in block 804 is shortened to the nearest lower prime number ofsamples, N_(p). In block 807, the N_(p)-length sequence is generated. Inblock 808, the N_(p) time samples are converted into N_(p) frequencytones. The N_(p) frequency tones are mapped onto the allocatedrandom-access channel sub-carriers in block 810. Because N_(pi)sub-carriers are allocated to the random-access channel, and thepreamble sequence length was shortened to N_(p) samples resulting inonly N_(p) frequency tones to be mapped onto the sub-carriers,N_(pi)-N_(p) sub-carriers remain unused. In block 812, the unusedsub-carriers are zeroed and distributed around the preamble sub-carriersto provide isolation from adjacent frequency bands. These unusedsub-carriers can be potentially be re-used for cubic metric (or PAPR)reduction through either cyclic extension or tone reservation.

FIG. 9 shows a flow diagram of an alternative method of generating aprime length sequence for use with an SC-FDMA up-link transmitter.Because the preamble sequence is deterministic, prime length preamblesequences can be predefined and stored for later use.

In block 900, a RACH message 3 threshold value encoded as a two or threebit value is received from the serving NodeB via an SIB. The thresholdvalue is calculated by the NodeB as described with respect to equation5.

In block 902, once configured by the Node B, the prime length preamblesequences are generated and converted into frequency domain preamblesamples. In block 904, the frequency domain preamble samples are storedin a storage device to be retrieved as needed. In block 906, a randomaccess signal transmission is initiated, and preamble duration isselected. The selected duration is an integer multiple of up-linksub-carrier data block duration, and is chosen to meet system coveragerequirements.

The UE then uses the threshold value to determine in block 908 itsrequested message 3 length as described in more detail with regard toequation 6. Since there are two choices for the message 3 length, the UEforms the preamble by selecting from one of two defined sets ofsequences in order to convey the preferred message 3 size to the NodeB.

In block 910, a stored preamble sequence is selected. The selectedsequence will preferably be the sequence having the number of samplesimmediately lower than the number of samples computed from the durationselected in block 906 and random access signal bandwidth. In block 912,the preamble frequency samples are read from the storage device andmapped onto the sub-carriers allocated to the random access channel.Because more sub-carriers are allocated to the random access channelthan there are preamble frequency samples, unused sub-carriers arezeroed and distributed in block 914 around the preamble sub-carriers toprovide isolation from adjacent frequency bands. This alternateimplementation allows omission of the frequency domain transformingcomponent 402 from the random access preamble transmitter. The preamblesamples are frequency domain transformed only once, prior to storage,and therefore the transform process is not concerned with the latencyrequirements of the random access preamble transmitter, and can beimplemented in a simpler and less costly manner. It should be furthernoted that frequency domain transforming component 402 can be totallyeliminated if the preamble root sequence is configured directly infrequency representation by the Node B. However, because the preamblesequence is defined to be a Cyclic Shifted Zadoff-Chu sequence, thecyclic shift must still be implemented. The cyclic shift may beperformed at the system sampling rate before cyclic prefix insertion410.

For orthogonal multiplexing in Orthogonal Frequency Division Multiplexed(“OFDM”) systems, each tone carries a modulated symbol according to afrequency overlapped time limited orthogonal structure. The frequencytones overlap with each other so that in the center of a tone, thespectral envelopes of all surrounding tones are null. This principleallows multiplexing of different transmissions in the same systembandwidth in an orthogonal manner. However, this only holds true if thesub-carrier spacing δf is kept constant. δf is equal to the inverse ofthe OFDM symbol duration T, used to generate the frequency tones by DFT.Because the preamble OFDM symbol is longer than the data OFDM symbol,the sub-carrier spacing of the preamble OFDM symbol will be shorter thanthe sub-carrier spacing of the data OFDM symbol. In addition, since dataand preamble OFDM symbols are neither aligned nor have same durations,strict orthogonality cannot be achieved. However, the following designrules aim at minimizing the co-interference between preamble and dataOFDM symbols: 1) fixing the preamble OFDM symbol duration to an integermultiple of the data symbol duration provides some commensurabilitybetween preamble and data sub-carriers thus providing interferencereduction between these sub-carriers, and 2) this also assumes that thepreamble sampling frequency is an integer multiple of the data symbolsub-carrier spacing.

In OFDM systems, different UEs' transmissions are dynamically allocatedto different non overlapping frequency bands. This allocation isgenerally based on a minimum frequency granularity, called a resourceblock (RB). In order to facilitate the frequency multiplexing of therandom access preamble and the data transmission, the preamble should beallocated an integer number of resource blocks

In addition to the detection process, random access preamble 304 allowsbase station 101 to analyze the frequency response of up-link 111, overa range of frequencies within the preamble bandwidth. Characterizationof up-link 111 frequency response allows base station 101 to tailor thenarrow band up-link 111 resources allocated to UE 109 within thepreamble bandwidth to match up-link 111 frequency response, resulting inmore efficient utilization of up-link resource.

System Example

FIG. 10 is a block diagram illustrating operation of a NodeB 1002 and amobile UE 1001 in the network system of FIG. 1. The mobile UE device1001 may represent any of a variety of devices such as a server, adesktop computer, a laptop computer, a cellular phone, a PersonalDigital Assistant (PDA), a smart phone or other electronic devices. Insome embodiments, the electronic mobile UE device 1001 communicates withthe NodeB 1002 based on a LTE or E-UTRAN protocol. Alternatively,another communication protocol now known or later developed can be used.

As shown, the mobile UE device 1001 comprises a processor 1010 coupledto a memory 1012 and a Transceiver 1020. The memory 1012 stores(software) applications 1014 for execution by the processor 1010. Theapplications could comprise any known or future application useful forindividuals or organizations. As an example, such applications could becategorized as operating systems (OS), device drivers, databases,multimedia tools, presentation tools, Internet browsers, e-mailers,Voice-Over-Internet Protocol (VOIP) tools, file browsers, firewalls,instant messaging, finance tools, games, word processors or othercategories. Regardless of the exact nature of the applications, at leastsome of the applications may direct the mobile UE device 1001 totransmit UL signals to the NodeB (base-station) 1002 periodically orcontinuously via the transceiver 1020. In at least some embodiments, themobile UE device 1001 identifies a Quality of Service (QoS) requirementwhen requesting an uplink resource from the NodeB 1002. In some cases,the QoS requirement may be implicitly derived by the NodeB 1002 from thetype of traffic supported by the mobile UE device 1001. As an example,VOIP and gaming applications often involve low-latency uplink (UL)transmissions while High Throughput (HTP)/Hypertext TransmissionProtocol (HTTP) traffic can involve high-latency uplink transmissions.

Transceiver 1020 includes uplink logic which may be implemented byexecution of instructions that control the operation of the transceiver.Some of these instructions may be stored in memory 1012 and executedwhen needed by processor 1010. As would be understood by one of skill inthe art, the components of the Uplink Logic may involve the physical(PHY) layer and/or the Media Access Control (MAC) layer of thetransceiver 1020. Transceiver 1020 includes one or more receivers 1022and one or more transmitters 1024.

Processor 1010 may send or receive data to various input/output devices1026. A subscriber identity module (SIM) card stores and retrievesinformation used for making calls via the cellular system. A Bluetoothbaseband unit may be provided for wireless connection to a microphoneand headset for sending and receiving voice data. Processor 1010 maysend information to a display unit for interaction with a user of themobile UE during a call process. The display may also display picturesreceived from the network, from a local camera, or from other sourcessuch as a USB connector. Processor 1010 may also send a video stream tothe display that is received from various sources such as the cellularnetwork via RF transceiver 1022 or the camera.

During transmission and reception of voice data or other applicationdata, transmitter 1024 may be or become non-synchronized with itsserving NodeB. In this case, it sends a random access signal asdescribed in more detail with respect to FIGS. 2-9. As part of thisprocedure, it determines a preferred size for the next datatransmission, referred to as message 3, by using a power threshold valueprovided by the serving NodeB, as described in more detail above. Inthis embodiment, the message 3 preferred size determination is embodiedby executing instructions stored in memory 1012 by processor 1010. Inother embodiments, the message 3 size determination may be embodied by aseparate processor/memory unit, by a hardwired state machine, or byother types of control logic, for example.

NodeB 1002 comprises a Processor 1030 coupled to a memory 1032, symbolprocessing circuitry 1038, and a transceiver 1040 via backplane bus1036. The memory stores applications 1034 for execution by processor1030. The applications could comprise any known or future applicationuseful for managing wireless communications. At least some of theapplications 1034 may direct the base-station to manage transmissions toor from the user device 1001.

Transceiver 1040 comprises an uplink Resource Manager, which enables theNodeB 1002 to selectively allocate uplink PUSCH resources to the userdevice 1001. As would be understood by one of skill in the art, thecomponents of the uplink resource manager may involve the physical (PHY)layer and/or the Media Access Control (MAC) layer of the transceiver1040. Transceiver 1040 includes a Receiver(s) 1042 for receivingtransmissions from various UE within range of the NodeB andtransmitter(s) 1044 for transmitting data and control information to thevarious UE within range of the NodeB.

The uplink resource manager executes instructions that control theoperation of transceiver 1040. Some of these instructions may be locatedin memory 1032 and executed when needed on processor 1030. The resourcemanager controls the transmission resources allocated to each UE that isbeing served by NodeB 1002 and broadcasts control information via thephysical downlink control channel PDCCH.

Symbol processing circuitry 1038 performs demodulation using knowntechniques. Random access signals are demodulated in symbol processingcircuitry 1038 as described in more detail above with regard to FIG. 7.

During transmission and reception of voice data or other applicationdata, receiver 1042 may receive a random access signal from a UE, asdescribed in more detail above. The random access signal is encoded torequest a message 3 size that is preferred by the UE. The UE determinesthe preferred message 3 size by using a message 3 threshold provided bythe NodeB. In this embodiment, the message 3 threshold calculation isembodied by executing instructions stored in memory 1032 by processor1030. In other embodiments, the threshold calculation may be embodied bya separate processor/memory unit, by a hardwired state machine, or byother types of control logic, for example. Alternatively, in somenetworks the message 3 threshold is a fixed value that may be stored inmemory 1032, for example. In response to receiving the message 3 sizerequest, the NodeB schedules an appropriate set of resources andnotifies the UE with a resource grant.

Other Embodiments

While the invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various other embodiments of the invention will beapparent to persons skilled in the art upon reference to thisdescription. For example, more than two message 3 sizes may be allowedand encoded in the RA preamble.

Embodiments of the described invention applies to any systems whererandom access signaling is implemented, including but not limited toTDD, FDD, and HD-FDD systems.

The term “frame” and “subframe” are not restricted to the structure ofFIG. 2 and FIG. 3. Other configurations of frames and/or subframes maybe embodied. In general, the term “frame” may refer to a set of one ormore subframes. A transmission instance likewise refers to a frame,subframe, or other agreed upon quantity of transmission resource.

An embodiment of the invention may include a system with a processorcoupled to a computer readable medium in which a software program isstored that contains instructions that when executed by the processorperform the functions of modules and circuits described herein. Thecomputer readable medium may be memory storage such as dynamic randomaccess memory (DRAM), static RAM (SRAM), read only memory (ROM),Programmable ROM (PROM), erasable PROM (EPROM) or other similar types ofmemory. The computer readable media may also be in the form of magnetic,optical, semiconductor or other types of discs or other portable memorydevices that can be used to distribute the software for downloading to asystem for execution by a processor. The computer readable media mayalso be in the form of magnetic, optical, semiconductor or other typesof disc unit coupled to a system that can store the software fordownloading or for direct execution by a processor.

As used herein, the terms “applied,” “coupled,” “connected,” and“connection” mean electrically connected, including where additionalelements may be in the electrical connection path. “Associated” means acontrolling relationship, such as a memory resource that is controlledby an associated port.

It is therefore contemplated that the appended claims will cover anysuch modifications of the embodiments as fall within the true scope andspirit of the invention.

APPENDIX A messagePowerOffsetGroupB = ΔTF + 10log10 (N_(RB)) + margin(=0) (dB) N_(sc) ^(RB) 12 N_(symb) ^(PUSCH) 6 N_(RB) 1 0 dB N_(RB) 23.01 dB Nre 144 messagePowerOf Nre 288 messagePowerOf I_(TBS) Mod msg3TBS MPR ΔTF (dB) fsetGroupB (dB) Mod msg3 TBS MPR ΔTF (dB) fsetGroupB(dB) 0 2 16 0.11 −9.95 −9.95 2 32 0.11 −9.95 −6.94 1 2 24 0.17 −8.09−8.09 2 56 0.19 −7.36 −4.35 2 2 32 0.22 −6.73 −6.73 2 72 0.25 −6.16−3.15 3 2 40 0.28 −5.65 −5.65 2 104 0.36 −4.35 −1.34 4 2 56 0.39 −3.97−3.97 2 120 0.42 −3.62 −0.61 5 2 72 0.50 −2.66 −2.66 2 144 0.50 −2.660.35 6 2 na 2 176 0.61 −1.56 1.45 7 2 104 0.72 −0.61 −0.61 2 224 0.78−0.17 2.84 8 2 120 0.83 0.25 0.25 2 256 0.89 0.65 3.66 9 2 136 0.94 1.031.03 2 286 0.99 1.35 4.36 10 2/4 144 1.00 1.39 1.39 2/4 328 1.14 2.265.27 11 4 176 1.22 2.75 2.75 4 376 1.31 3.22 6.23 12 4 208 1.44 3.973.97 4 440 1.53 4.40 7.42 13 4 224 1.56 4.55 4.55 4 488 1.69 5.24 8.2514 4 256 1.78 5.64 5.64 4 552 1.92 6.30 9.31 15 4/6 280 1.94 6.43 6.434/6 600 2.08 7.06 10.07 N_(RB) 3 4.77 dB N_(RB) 4 6.02 dB Nre 432messagePowerOf Nre 576 messagePowerOf I_(TBS) Mod msg3 TBS MPR ΔTF (dB)fsetGroupB (dB) Mod msg3 TBS MPR ΔTF (dB) fsetGroupB (dB) 0 2 56 0.13−9.25 −4.48 2 88 0.15 −8.49 −2.47 1 2 88 0.20 −7.14 −2.37 2 144 0.25−6.16 −0.14 2 2 144 0.33 −4.75 0.02 2 176 0.31 −5.18 0.84 3 2 176 0.41−3.73 1.04 2 208 0.36 −4.35 1.67 4 2 208 0.48 −2.86 1.91 2 256 0.44−3.28 2.74 5 2 224 0.52 −2.46 2.31 2 328 0.57 −1.95 4.07 6 2 256 0.59−1.73 3.04 2 392 0.68 −0.95 5.07 7 2 328 0.76 −0.31 4.46 2 472 0.82 0.156.17 8 2 392 0.91 0.77 5.55 2 536 0.93 0.93 6.95 9 2 456 1.06 1.75 6.522 616 1.07 1.84 7.86 10 2/4 504 1.17 2.43 7.20 2/4 680 1.18 2.51 8.53 114 584 1.35 3.48 8.25 4 776 1.35 3.45 9.47 12 4 680 1.57 4.64 9.41 4 9041.57 4.62 10.64 13 4 744 1.72 5.37 10.15 4 1000 1.74 5.44 11.46 14 4 8401.94 6.43 11.20 4 1128 1.96 6.49 12.51 15 4/6 904 2.09 7.10 11.87 4/61224 2.13 7.25 13.27 N_(RB) 5 6.99 dB Nre 720 messagePowerOf I_(TBS) Modmsg3 TBS MPR ΔTF (dB) fsetGroupB (dB) 0 2 120 0.17 −8.09 −1.10 1 2 1760.24 −6.27 0.72 2 2 208 0.29 −5.46 1.53 3 2 256 0.36 −4.43 2.56 4 2 3280.46 −3.15 3.84 5 2 424 0.59 −1.77 5.22 6 2 504 0.70 −0.79 6.20 7 2 5840.81 0.08 7.07 8 2 680 0.94 1.03 8.02 9 2 776 1.08 1.89 8.88 10 2/4 8721.21 2.69 9.67 11 4 1000 1.39 3.68 10.67 12 4 1128 1.57 4.60 11.59 13 41256 1.74 5.48 12.47 14 4 1416 1.97 6.53 13.52 15 4/6 1544 2.14 7.3314.32

APPENDIX B Power control of Msg3 P_(Msg3) = min(P_(max); 10log10(N_(RB)) + Po_pre + Δ_(Preamble)_msg3 + PL + Δ_(TF) + Δ_(prampup) (=0) +δmsg2 (=0)) UE: cNB distance (km) 1 1.5 2 2.5 3 3.5 4 4.5 5 Pathloss(dB) Msg3 Allocation 125.492 131.6948 136.095786 139.5094 142.2986144.6568 146.6995 148.5014 150.1132 Modulation TBS P_(Msg3) (dBm)N_(RB,Msg3) = 1 QPSK 104 0.487073 6.689862 11.0908111 14.50445 17.293619.65179 21.69455 23 23 QPSK 120 1.340903 7.543692 11.9446415 15.3582818.14743 20.50562 22.54838 23 23 QPSK 136 2.1201 8.322889 12.723837716.13748 18.92663 21.28482 23 23 23 QPSK/16QAM 144 2.487363 8.69015313.0911017 16.50474 19.29389 21.65208 23 23 23 16QAM 176 3.84302310.04581 14.4467612 17.8604 20.64955 23 23 23 23 16QAM 208 5.06538111.26817 15.6691191 19.08276 21.87191 23 23 23 23 16QAM 224 5.64033111.84312 16.2440692 19.65771 22.44686 23 23 23 23 16QAM 256 6.73562812.93842 17.3393664 20.75301 23 23 23 23 23 16QAM/64QAM 280 7.5192113.722 18.1229484 21.53659 23 23 23 23 23 N_(RB,Msg3) = 2 QPSK 104−0.24526 5.957526 10.3584753 13.77212 16.56126 18.91946 20.9622122.76405 23 QPSK 120 0.486599 6.689388 11.0903374 14.50396 17.2931319.65132 21.69408 23 23 QPSK 144 1.445548 7.648337 12.049286 15.4629318.25208 20.61027 22.65302 23 23 QPSK 176 2.542804 8.745593 13.146542316.56018 19.34933 21.70752 23 23 23 QPSK 224 3.934985 10.1377714.5387236 17.95236 20.74151 23 23 23 23 QPSK 256 4.748893 10.9516815.3526313 18.76627 21.55542 23 23 23 23 QPSK 286 5.452476 11.6552716.0562143 19.46986 22.259 23 23 23 23 QPSK/16QAM 328 6.363575 12.5663616.967313 20.38095 23 23 23 23 23 16QAM 376 7.32462 13.52741 17.928358321.342 23 23 23 23 23 16QAM 440 8.508812 14.7116 19.1125507 22.52619 2323 23 23 23 16QAM 488 9.342741 15.54553 19.946479 23 23 23 23 23 2316QAM 552 10.40083 16.60362 21.004564 23 23 23 23 23 23 16QAM/64QAM 60011.16285 17.36564 21.7665848 23 23 23 23 23 23 N_(RB,Msg3) = 3 QPSK 1441.11315 7.315939 11.7168882 15.13053 17.91968 20.27787 22.32063 23 23QPSK 176 2.131456 8.334246 12.7351966 16.14884 18.93799 21.29618 23 2323 QPSK 208 3.005253 9.208042 13.6089913 17.02283 19.81178 22.16997 2323 23 QPSK 224 3.401798 9.604588 14.0055367 17.41918 20.20833 22.5665223 23 23 QPSK 256 4.132221 10.33501 14.7359594 18.1496 20.93875 23 23 2323 QPSK 328 5.552564 11.75535 16.156302 19.56994 22.35909 23 23 23 23QPSK 392 6.63867 12.84146 17.2424077 20.65605 23 23 23 23 23 QPSK 4567.613223 13.81601 18.2169613 21.6306 23 23 23 23 23 QPSK/16QAM 5048.289963 14.49275 16.8937007 22.30734 23 23 23 23 23 16QAM 584 9.34032815.54312 19.9440866 23 23 23 23 23 23 16QAM 680 10.50542 16.7082121.1091615 23 23 23 23 23 23 16QAM 744 11.23898 17.44177 21.8427174 2323 23 23 23 23 16QAM 840 12.29042 18.49321 22.8941609 23 23 23 23 23 2316QAM/64QAM 904 12.96543 19.16822 23 23 23 23 23 23 23 N_(RB,Msg3) = 4QPSK 144 0.949767 7.152556 11.5535053 14.96715 17.75629 20.1144922.15724 23 23 QPSK 176 1.929982 8.132771 12.53372 15.94736 18.7365121.0947 23 23 23 QPSK 208 2.765037 8.967826 13.3687753 16.78242 19.5715621.92976 23 23 23 QPSK 256 3.83269 10.03548 14.4364286 17.85007 20.6392222.99741 23 23 23 QPSK 328 5.161369 11.36416 15.7651076 19.17875 21.957923 23 23 23 QPSK 392 6.163315 12.3661 16.7670536 20.18069 22.96984 23 2323 23 QPSK 472 7.259288 13.46208 17.8630259 21.27657 23 23 23 23 23 QPSK536 8.046728 14.24952 18.6504661 22.06411 23 23 23 23 23 QPSK 6168.949467 15.15226 19.5532049 22.96685 23 23 23 23 23 QPSK/16QAM 6809.621231 15.82402 20.2249696 23 23 23 23 23 23 16QAM 776 10.5644516.76724 21.168185 23 23 23 23 23 23 16QAM 904 11.73139 17.9341822.3351276 23 23 23 23 23 23 16QAM 1000 12.55567 18.75846 23 23 23 23 2323 23 16QAM 1128 13.60389 19.80668 23 23 23 23 23 23 23 16QAM/64QAM 122414.36014 20.56293 23 23 23 23 23 23 23 N_(RB,Msg3) = 5 QPSK 120 −0.003556.199243 10.6001922 14.01383 16.80298 19.16117 21.20393 23 23 QPSK 1761.810444 8.013233 12.4141818 15.82782 18.61697 20.97516 23 23 23 QPSK208 2.622787 8.825576 13.226525 16.64017 19.42931 21.78751 23 23 23 QPSK256 3.655811 9.8586 14.2595492 17.67319 20.46234 22.82053 23 23 23 QPSK328 4.931289 11.13408 15.5350273 18.94667 21.73782 23 23 23 23 QPSK 4246.31592 12.51871 16.9196582 20.3333 23 23 23 23 23 QPSK 504 7.29496913.49776 17.8987069 21.31235 23 23 23 23 23 QPSK 584 8.166487 14.3692818.770225 22.18387 23 23 23 23 23 QPSK 680 9.1098 15.31259 19.7135378 2323 23 23 23 23 QPSK 776 9.970352 16.17314 20.57409 23 23 23 23 23 23QPSK/16QAM 872 10.76855 16.97134 21.3722879 23 23 23 23 23 23 16QAM 100011.75936 17.96215 22.363097 23 23 23 23 23 23 16QAM 1128 12.6864218.88921 23 23 23 23 23 23 23 16QAM 1256 13.56505 19.76784 23 23 23 2323 23 23 16QAM 1416 14.61135 20.81414 23 23 23 23 23 23 23 16QAM/64QAM1544 15.41606 21.61885 23 23 23 23 23 23 23 Pathloss model: % 1)Okumura - Hata emphical distance-dependent path loss mode defined in: %M, Shafi, S, Ogese and T. Hattori, Wireless Communications in the 21stCentury, IEEE press, Wiley-Interscience, 2002 pl = 69.55 + 26.16 * log10(f) − 13.82 * log10 (hb) − (3.2 * (log10 (11.75 * nm)){circumflex over( )}2 − 4.97) + (44.9 − 6.55 * log10 (hb)) * log10 (d) − (2 − 19 * log10(alpha)); % k (hm) is the correction factor for UE antenna height %alpha: The ground cover factor alpha is defined as the percentage of thearea covered by buildings, % f is the carrier frequency (MHz), Range:400-2200 MHz % hb is the Node-B antenna height (m), Range: 30-200 m % hmis the UE antenna height in meters (m). Range: 1-10 m % d is thedistance betw Range: 1-20 km % % A typical configuration is: % f = 2000MHz, % hb = 30/50 m, % hm = 1.5 m, 1.5 % alpha = 10% % 2) TR25.814;128.1 + 37.6log10 (r) x in km Parameters Name Value Unit RangeMeaning 1) Pathloss and link Type Okumura NA 25.814 or Type of pathlossmodel used budget Okumura Nrx 5 dB Receiver Noise Figure LF 0 dB  [0, 8]Log-Normal Fade Margin PI 0 dB  [0, 20] Penetration loss f 2000 MHzCarrier frequency hm 1.5 m UE height alpha 10 % hb 30 m eNB antennaheight T_(K) 308.15 ° K Temperature (308.15° K = 35° C.) K 1.38E−23Boltzmann constant N₀ −173.71 dBm/Hz Noise Power Density N −108.38 dBmNoise Power I 3.00 dB Interference margin E_(p)/N₀ 18 dB Target (total)preamble energy to noise density ratio E_(c)/N₀ (=C/N) −11.2376 dBTarget preamble subcarrier energy to noise density ratio at eNB antennaport 2) Power control Pmax 23 dBm [−40, 23] UE max transmit powerP_(o)_po −116.62 dBm [−120, −90] Received preamble power at antenna portΔPreamble_Msg3 −7.78 dB Po_pre_min −120 dBm

What is claimed is:
 1. A method for selecting a transport block size(TBS) of a first uplink message (RACH Msg3) transmitted on a PhysicalUplink Shared Channel (PUSCH) during a random access procedure in a UserEquipment (UE) accessing a radio access network, comprising: receiving apathloss threshold parameter; estimating a downlink pathloss valueindicative of radio link conditions between the UE and a base station(eNB) serving the UE; selecting from a set of TBS values a smaller valueof TBS if the determined pathloss value is greater than an operatingpower level of the UE minus the pathloss threshold parameter; sending arandom access request containing an indication of the selected TBS;wherein the operating power level of the UE is Pmax−P₀ _(—)_(PRE)−Δ_(PREAMBLE-Msg3); wherein the pathloss is the downlink pathlossvalue estimate calculated in the UE; wherein Pmax is the maximum allowedtransmission power; wherein P₀ _(—) _(PRE) is the initial targetreceived preamble power at the serving eNB antenna port; whereinΔ_(PREAMBLE-Msg3) is the offset between RACH preamble and the RACH Msg3;and wherein the pathloss threshold parameter is configured by thenetwork.
 2. The method of claim 1 wherein the parameters Pmax, P₀ _(—)_(PRE) and Δ_(PREAMBLE-Msg3), are configured by the network andbroadcasted as system information on a broadcast channel.
 3. The methodof claim 2 wherein the parameters Pmax, P₀ _(—) _(PRE) andΔ_(PREAMBLE-Msg3) are also used to set the transmission power Pmsg3 ofRACH Msg3 as follows:Pmsg3=min{Pmax;10 log₁₀(NRB+P ₀ _(—) _(PRE)+Δ_(PREAMBLE-Msg3) +PL+ΔP};wherein NRB is the size of a frequency allocation in resource blocks(RB) for RACH Msg3, PL is the downlink pathloss estimate determined bythe UE and ΔP is an optional adjustment factor accounting for variouscontributors such as power rampup of the preamble during potentialretries and MCS-dependent power offset.
 4. The method of claim 1 whereinthe threshold parameter is computed at the eNB as follows:THRESHOLD=Δ_(TF) _(—) _(B)+10 log₁₀(N _(RB) _(—) _(B))+margin whereinN_(RB-B) is the size of a frequency allocation in resource blocks (RB)for the RACH Msg3 associated with the larger TBS value; wherein ΔTF-B isa MCS-dependent power offset in use with the RACH Msg3 associated withthe larger TBS value; and wherein the margin value is a parameter thenetwork uses to tune the conservativeness of the selection process,allowing minimizing the rate of erroneous selection of the larger TBSvalue.
 5. The method of claim 4 wherein the threshold parameter is codedon three bits and broadcasted as system information on the broadcastchannel.
 6. The method of claim 5, wherein the threshold parameter ismapped on the three bit field, such that: a field value of 0 indicates aparameter value (dB) of −∞, a field value of 1 indicates a parametervalue (dB) of 0, a field value of 2 indicates a parameter value (dB) of3, a field value of 3 indicates a parameter value (dB) of 6, a fieldvalue of 4 indicates a parameter value (dB) of 9, a field value of 5indicates a parameter value (dB) of 12, a field value of 6 indicates aparameter value (dB) of 15, and a field value of 7 indicates a parametervalue (dB) of
 18. 7. A method for selecting a transport block size (TBS)of a first uplink message (RACH Msg3) transmitted on a Physical UplinkShared Channel (PUSCH) during a random access procedure in a UserEquipment (UE) accessing a radio access network, comprising: determininga pathloss threshold parameter by a base station (eNB) serving the UE;broadcasting the pathloss threshold parameter to a UE being served bythe eNB; and receiving a random access request from the UE with anindication of a selected TBS, wherein a smaller value of TBS is selectedfrom a set of TBS values by the UE if an estimated pathloss valueindicative of radio link conditions between the UE and the eNB isgreater than an operating power level of the UE minus the pathlossthreshold parameter; wherein a larger value of TBS is selected from theset of TBS values by the UE if the pathloss value is less than thepathloss threshold parameter and the TBS required to transmit the RACHMsg3 exceeds the smaller TBS value; wherein the threshold parameter iscomputed by the eNB as follows:THRESHOLD=Δ_(TF) _(—) _(B)+10 log₁₀(N _(RB) _(—) _(B))+margin whereinN_(RB-B) is the size of a frequency allocation in resource blocks (RB)for the RACH Msg3 associated with the larger TBS value; wherein ΔTF-B isa MCS-dependent power offset in use with the RACH Msg3 associated withthe larger TBS value; and wherein the margin value is a parameter thenetwork uses to tune the conservativeness of the selection process,allowing minimizing the rate of erroneous selection of the larger TBSvalue.
 8. The method of claim 7 wherein the threshold parameter is codedon three bits and broadcasted as system information on the broadcastchannel.
 9. The method of claim 8, wherein the threshold parameter ismapped on the three bit field, such that: a field value of 0 indicates aparameter value (dB) of −∞, a field value of 1 indicates a parametervalue (dB) of 0, a field value of 2 indicates a parameter value (dB) of3, a field value of 3 indicates a parameter value (dB) of 6, a fieldvalue of 4 indicates a parameter value (dB) of 9, a field value of 5indicates a parameter value (dB) of 12, a field value of 6 indicates aparameter value (dB) of 15, and a field value of 7 indicates a parametervalue (dB) of
 18. 10. A User Equipment (UE) apparatus for accessing aradio access network, the UE comprising: processing logic connected to amemory; radio frequency (RF) transmission logic coupled to theprocessing logic; and RF receiver logic couple to the processing logic,the RF receiving logic configured to receive a pathloss thresholdparameter; and wherein the processing logic is configured to select atransport block size (TBS) of a first uplink message (RACH Msg3)transmitted on a Physical Uplink Shared Channel (PUSCH) during a randomaccess procedure while the UE is accessing a radio access network by:estimating a downlink pathloss value indicative of radio link conditionsbetween the UE and a base station (eNB) serving the UE; selecting from aset of TBS values a smaller value of TBS if the determined pathlossvalue is greater than an operating power level of the UE minus thepathloss threshold parameter; sending a random access request via the RFtransmission logic containing an indication of the selected TBS; whereinthe processor is configured to select a larger value of TBS from the setof TBS values if the pathloss value is less than the operating powerlevel of the UE minus the pathloss threshold parameter and the TBSrequired to transmit the RACH Msg3 exceeds the smaller TBS value;wherein the operating power level of the UE is Pmax−P₀ _(—)_(PRE)−Δ_(PREAMBLE-Msg3); wherein the pathloss is the downlink pathlossestimate calculated in the UE; wherein Pmax is the maximum allowedtransmission power; wherein P₀ _(—) _(PRE) is the initial targetreceived preamble power at the serving eNB antenna port; whereinΔ_(PREAMBLE-Msg3) is the offset between RACH preamble and the RACH Msg3;and wherein the pathloss threshold parameter is received by the RFreceiver.
 11. The UE of claim 10 wherein the parameters Pmax, P₀ _(—)_(PRE) and Δ_(PREAMBLE-Msg3) are also used by the processor to set thetransmission power Pmsg3 of RACH Msg3 as follows:Pmsg3=min{Pmax;10 log₁₀(NRB+P ₀ _(—) _(PRE)+Δ_(PREAMBLE-Msg3) +PL+ΔP};wherein NRB is the size of a frequency allocation in resource blocks(RB) for RACH Msg3, PL is the downlink pathloss estimate determined bythe UE and LP is an optional adjustment factor accounting for variouscontributors such as power rampup of the preamble during potentialretries and MCS-dependent power offset.